While conventional brush commutated DC motors have numerous advantageous characteristics such as convenience of changing operational speeds and direction of rotation, it is believed that there are disadvantages such as brush wear, electrical noise or RF interference caused by sparking between the brushes and the segmented commutator, that have limited their applicability in some fields such as in the domestic appliance fields. Brushless DC motors with electronic commutation and permanent magnet rotors have now been developed and generally are believed to have the advantageous characteristics of the brush-type motors without many of the disadvantages thereof and have other important advantages. Such electronically commutated motors are disclosed in the David M. Erdmann U.S. Pat. Nos. 4,005,347 and 4,169,990 and Floyd H. Wright U.S. Pat. No. 4,162,435. These motors may be advantageously employed in many different fields or motor applications among which are domestic commercial appliances, e.g., automatic washing or laundry machines such as disclosed in co-pending U.S. patent applications, Ser. No. 077,784, filed Sept. 21, 1979 and Ser. No. 141,268, filed Apr. 17, 1980.
Laundry machines as there disclosed are believed to have many significant advantages over present day laundry machines which employ various types of transmissions and mechanisms to convert rotary motion into oscillatory motion to selectively actuate the machine in its agitation or washing mode and in its spin extraction mode and which are believed to be more costly and/or complicated to manufacture and consume more energy and require more servicing. Laundry machines with electronically commutated motors require no mechanical means to effect oscillatory action of the agitator and the spin basket may be directly driven by such a motor. However, it is believed that the high torque which must be developed at low speeds during the agitation cycle and the high speed relatively low torque requirements for the spin cycle impose certain practical limitations on the design and manufacture of such machines. To accommodate these different requirements it is believed that a multiple drive path transmission with a greater ratio speed reduction for the wash cycle had to be provided or higher currents had to be supplied to the motor. Each of these alternatives is believed to have disadvantages, particularly the increased costs entailed. In the latter instance, it is believed that larger and more expensive semi-conductor devices would be required to handle higher current requirements.